A&A 514, A1 (2010) Astronomy DOI: 10.1051/0004-6361/200913811 & c ESO 2010 Astrophysics Science with AKARI Special feature The AKARI/IRC mid-infrared all-sky survey D. Ishihara1,2, T. Onaka2, H. Kataza3,A.Salama4, C. Alfageme4,, A. Cassatella4,5,6,N.Cox4,, P. García-Lario4, C. Stephenson4,†,M.Cohen7, N. Fujishiro3,8,‡, H. Fujiwara2, S. Hasegawa3,Y.Ita9,W.Kim3,2,§, H. Matsuhara3, H. Murakami3,T.G.Müller10, T. Nakagawa3, Y. Ohyama11,S.Oyabu3,J.Pyo12,I.Sakon2, H. Shibai13,S.Takita3, T. Tanabé14,K.Uemizu3,M.Ueno3,F.Usui3,T.Wada3, H. Watarai15, I. Yamamura3, and C. Yamauchi3 1 Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-860, Japan e-mail: [email protected] 2 Department of Astronomy, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan 3 Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara, Kanagawa, 229-8510, Japan 4 European Space Astronomy Center (ESAC), Villanueva de la Cañada, PO Box 78, 28691 Madrid, Spain 5 INAF, Istituto di Fisica dello Spazio Interplanetario, via del Fosso del Cavaliere 100, 00133 Roma, Italy 6 Dipartimento di Fisica, Universita’ Roma Tre, via della Vasca Navale 100, 00146 Roma, Italy 7 Radio Astronomy Laboratory, University of California, Berkeley, USA 8 Department of Physics, Faculty of Science, University of Tokyo, 3-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0003, Japan 9 National Astronomical Observatory of Japan, Mitaka, Tokyo, 181-8588, Japan 10 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraβe, 85748 Garching, Germany 11 Academia Sinica, Institute of Astronomy and Astrophysics (ASIAA), Taipei 10617, Taiwan 12 Korea Astronomy and Space Science Institute (KASI), 61-1, Hwaam-dong, Yuseong-gu, Daejeon, 305-348, Republic of Korea 13 Graduate School of Science, Osaka University, 1-1, Machikaneyama, Toyonaka, Osaka, 560-0043, Japan 14 Institute of Astronomy, Faculty of Science, University of Tokyo, Mitaka, Tokyo, 181-8588, Japan 15 Space Applications Mission Directorate, Japan Aerospace Exploration Agency (JAXA), 2-1-1, Sengen, Tsukuba, Ibaraki, 305-8505, Japan Received 6 December 2009 / Accepted 17 February 2010 ABSTRACT Context. AKARI is the first Japanese astronomical satellite dedicated to infrared astronomy. One of the main purposes of AKARI is the all-sky survey performed with six infrared bands between 9 μm and 200 μm during the period from 2006 May 6 to 2007 August 28. In this paper, we present the mid-infrared part (9 μm and 18 μm bands) of the survey carried out with one of the on-board instruments, the infrared camera (IRC). Aims. We present unprecedented observational results of the 9 μm and 18 μm AKARI all-sky survey and detail the operation and data processing leading to the point source detection and measurements. Methods. The raw data are processed to produce small images for every scan, and the point sources candidates are derived above the 5σ noise level per single scan. The celestial coordinates and fluxes of the events are determined statistically and the reliability of their detections is secured through multiple detections of the same source within milli-seconds, hours, and months from each other. Results. The sky coverage is more than 90% for both bands. A total of 877 091 sources (851 189 for 9 μm, 195 893 for 18 μm) are confirmed and included in the current release of the point source catalog. The detection limit for point sources is 50 mJy and 90 mJy for the 9 μm and 18 μm bands, respectively. The position accuracy is estimated to be better than 2. Uncertainties in the in-flight absolute flux calibration are estimated to be 3% for the 9 μm band and 4% for the 18 μm band. The coordinates and fluxes of detected sources in this survey are also compared with those of the IRAS survey and are found to be statistically consistent. Key words. infrared: general – techniques: image processing – surveys Catalog is available in electronic form at the CDS via anonymous 1. Introduction ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/514/A1 Present address: INTA, Ctra. de Ajalvir km. 4. 28850 Torrejón de Unbiased and sensitive all-sky surveys at infrared wavelengths Ardoz, Madrid, Spain. are important for the various fields of astronomy. The first exten- Present address: Instituut voor Sterrenkunde, Katholieke sive survey of the mid- to far-infrared sky was made by the IRAS Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium. mission launched in 1983 (Neugebauer et al. 1984). IRAS sur- † Present address: Deimos Space S.L., Ronda de Poniente, 19, veyed 87% of the sky in four photometric bands at 12 μm, 25 μm, Edificio Fiteni VI, 28760 Tres Cantos, Madrid, Spain. μ μ ‡ 60 m and 100 m and substantially pioneered the various new Present address: Cybernet system Co. Ltd., 3 Kanda-neribeicho, fields of astronomy, like circumstellar debris disks around Vega- Chiyoda-ku, Tokyo, 101-0022, Japan. § like stars (Aumann et al. 1984) and a new class of galaxies that Present address: SONY Co. Ltd., 4-14-1, Asahi-cho, Atsugi-shi, radiate most of their energy in the infrared (Soifer et al. 1987). Kanagawa, 243-0014, Japan. Article published by EDP Sciences Page 1 of 14 A&A 514, A1 (2010) A decade later than IRAS, the Midcourse Space Experiment Table 1. Parameters for mid-infrared all-sky survey operation. (MSX; Price et al. 2001) surveyed the Galactic plane as well as the regions not observed by or confused in the IRAS mission Filter band (Camera) S 9W (MIR-S) L18W (MIR-L) with higher sensitivity and higher spatial resolution (18.3 )in ‡ μ μ four mid-infrared broad bands centered at 8.28 μm, 12.13 μm, Wavelength 6.7–11.6 m 13.9–25.6 m Isophotal wavelength 8.61 μm 18.39 μm 14.65 μm and 21.23 μm and two narrow bands at 4.29 μmand ff μ μ μ E ective bandwidth 4.10 m9.97m 4.35 m. The MSX catalog (version 1.2) of the Galactic plane Sampling rate (period) 22.27 Hz (44 ms) survey contains 323 052 sources, three times as many as IRAS Scan rate (exposure∗ ) 216 s−1 (11 ms) listed for the same region. Reset rate (period) 0.074 Hz (13.464 s) AKARI, the first Japanese space mission dedicated to in- Operation 256 × 2pix th th frared astronomical observations (Murakami et al. 2007), was Operated row 117 , 125 Binning 4 × 1pix launched in 2006 and was brought into a sun-synchronous po- Virtual pixel scale 9. 36 × 9. 36 10. 4 × 9. 36 lar orbit at an altitude of 700 km. It has two scientific instru- † † Detection limit (5σ)50mJy 120 mJy ments, the infrared camera (IRC; Onaka et al. 2007)for2−26 μm and the Far-Infrared Surveyor (FIS; Kawada et al. 2007)for Notes. (∗) Effective exposures for point sources are determined not by 50−200 μm. AKARI has a Ritchey-Chretien type cooled tele- the sampling rate, but by the dwelling time of a source on a pixel. scope with a primary-mirror aperture size of 685 mm (Kaneda (†) Estimated value from readout noise in shuttered configuration et al. 2007), which is operated at 6 K by liquid helium and in-orbit. mechanical coolers. One of the major observational objectives (‡) Defined as where the responsivity for a given energy is larger than 1/e of AKARI is an all-sky survey observation. The survey was of the peak. executed during the life time of the cooling medium between 2006 May 8 and 2007 August 28. The 9 μm and 18 μm bands of the IRC and the 65 μm, 90 μm, 140 μm, and 160 μm bands of 2.2. The infrared camera (IRC) the FIS were used for the all-sky survey. The mid-infrared component of the AKARI all-sky survey was In this paper, we present the mid-infrared part of the all- performed with one of the two focal-plane instruments: the IRC. sky survey performed with the IRC. The IRC was originally de- The IRC covers the wavelength range of 2−26 μm with three signed for imaging and spectroscopic observations in the point- independent channels: NIR (2−5.5 μm), MIR-S (6−12 μm) and ing mode, but the all-sky observation mode was added as an MIR-L (12−26 μm). The IRC was primarily designed for deep operation mode following ground tests, in which the acceptable imaging and spectroscopy in pointed observations. All the chan- performance of continuous survey-type observations was con- nels have filter wheels, which hold three filters and two spectro- firmed (Ishihara et al. 2006a). The data of the IRC all-sky survey scopic dispersers. Each channel has a large format array that pro- observation have been processed by a dedicated program and a vides a wide field-of-view (FOV) of 10 × 10 . The MIR-S and point source catalog has been prepared. The content of this pa- MIR-L channels have infrared sensor arrays of 256 × 256 pixels per is based on the β-1 version of the AKARI/IRC all-sky survey (Si:As/CRC-744 manufactured by Raytheon). The pixel scales point source catalog. for MIR-S and MIR-L are 2. 34 × 2. 34 and 2. 51 × 2. 39, re- spectively. The field-of-views of MIR-S and MIR-L are sepa- The outline of the observation is presented in Sect.